ABSTRACT While father engagement programming is widely advocated, few clinical and public health approaches engage fathers during the pre- and perinatal periods. A large body of literature shows that fathers play a key role in promoting child health and development beginning even before their children are born. Interventions to actively engage fathers, particularly early in pregnancy, have significant promise for improving infant outcomes (e.g., physical, social, and emotional health and development), the well-being of mothers and fathers, and transforming couples' relationships, especially among lower socioeconomic status (SES) individuals. However, readily scalable approaches that effectively translate evidence-based guidance to engage lower SES fathers during the prenatal period to improve infant and mother outcomes are lacking. Not engaging fathers not only fails men, but compromises the quality of care delivered to mothers and children. Our formative work demonstrates that lower SES fathers identify a variety of infant care knowledge, skill, and support gaps and are interested to receive such information via a text-messaging platform. Further, substantial research supports the use of text-message interventions for vulnerable and difficult-to-reach populations. Thus, a readily-scalable, easily adaptable intervention that could reach lower SES fathers has the potential to substantially impact child, parent, and family health at the population level. Text4Father, a multi-modal text messaging program, is designed to increase first-time lower SES fathers' knowledge, self-efficacy, and behavioral engagement on infant care and parenting. Text4Father consists of 48- weeks of twice weekly texts written at a 5th grade reading level. Texts include resource links and instructions to support behavior change (e.g., videos, infographics), starting mid-pregnancy and continuing through 6 months of postnatal age. Text content was developed using formative research and feedback from the target population, consensus building with experts, and an evidence-based review. Text4Father is programmed to push/receive reminders to tailor text content based on: gestational age, infant's birth, infant's age, and father's resident status. We propose to pilot test the first 24 weeks of the Text4Father curriculum (6-month follow-up through 1 month of postnatal age) to examine its feasibility, acceptability, and preliminary efficacy. Mobile health (mHealth) interventions have broad accessibility; the majority of Americans own a cellphone and use them to text and evidence supports using text messaging interventions, especially for difficult-to-reach populations. Advantages to using an mHealth approach is that it can be readily scalable for deployment via maternity providers, as proposed here, or to other settings (e.g., home visiting, WIC, pediatric care) and platforms (e.g., social media). If successful, this pilot will inform a larger trial that will evaluate the longer-term efficacy of engaging lower SES fathers through 48 weeks of the Text4Father curriculum (12-month follow-up through 6 months of postnatal age).